U.S. patent application number 10/479815 was filed with the patent office on 2004-09-23 for brazing material and brazed products manufactured therewith.
Invention is credited to Sjodin, Per Erik.
Application Number | 20040184945 10/479815 |
Document ID | / |
Family ID | 20284387 |
Filed Date | 2004-09-23 |
United States Patent
Application |
20040184945 |
Kind Code |
A1 |
Sjodin, Per Erik |
September 23, 2004 |
Brazing material and brazed products manufactured therewith
Abstract
An iron based brazing material for joining objects by brazing
represents an alloy, which apart from iron contains 0-40% Cr,
preferably 9-30% Cr, 0-16% Mn, preferably 0-8% Mn, and even more
preferably 0-5% Mn, 0-25% Ni, 0-1% N and maximally 7% Mo, below 6%
Si and/or 0-2% B, preferably 0-1.5% B and/or 0-15% P, all stated in
weight percent, which addition of B, P, Si in combination or
separately lowers the liquidus temperature, that is the temperature
at which the brazing material is completely melted. A brazed
product is manufactured by brazing of iron based objects with an
iron based brazing material which is alloyed with a liquidus
lowering element as B and/or P and/or Si.
Inventors: |
Sjodin, Per Erik; (Lund,
SE) |
Correspondence
Address: |
McCormick Paulding & Huber
City Place II
185 Asylum Street
Hartford
CT
06103-3402
US
|
Family ID: |
20284387 |
Appl. No.: |
10/479815 |
Filed: |
April 27, 2004 |
PCT Filed: |
June 3, 2002 |
PCT NO: |
PCT/SE02/01047 |
Current U.S.
Class: |
420/42 ; 420/46;
420/50 |
Current CPC
Class: |
C22C 38/002 20130101;
C22C 38/54 20130101; Y10T 428/12979 20150115; C22C 38/44 20130101;
C22C 38/58 20130101; C22C 38/34 20130101; C22C 38/56 20130101; B23K
35/3086 20130101; C22C 38/02 20130101 |
Class at
Publication: |
420/042 ;
420/046; 420/050 |
International
Class: |
C22C 038/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 2001 |
SE |
0102010.6 |
Claims
1. Iron based brazing material for joining objects by brazing,
characterized in that the brazing material consists of an alloy
which apart from iron contains 0-40% Cr, preferably 9-30% Cr, 0-16%
Mn, preferably 0-8% Mn, and even more preferably 0-5 Mn, 0-25% Ni,
0-1% N and maximally 7% Mo, below 6% Si, and/or 0-2% B, preferably
0-1.5% B and/or 0-15% P, all stated in weight percent, which
addition of B, P, Si in combination or separately lowers the
liquidus temperature, that is the temperature at which the brazing
material is completely melted.
2. Iron based brazing material according to claim 1, characterized
in that melting point lowering elements are added to the brazing
material in amounts according to the following formula
Index=%P+1.1.times.% Si+3.times.%B, where the value of the Index
should be 4.5 -18.
3. Iron based brazing material according to claim 1-2,
characterized in that the brazing material is manufactured by gas
or water atomising or crushing of an ingot with the composition
given above or melt spinning of a melt with such composition.
4. Iron based brazing material according to any of the preceding
claims, characterized in that the brazing material contains 0-20%
Hf and/or 0-2% C.
5. Brazed product manufactured by brazing of iron based objects,
characterized in that the objects are joined by an iron based
brazing material which is alloyed with a liquidus lowering element
as B and/or P and/or Si.
6. Brazed product according to claim 5, characterized in that both
the iron based objects and the iron based brazing material contains
9-30% Cr.
7. Brazed product according to claim 6, characterized in that the
product is a plate heat exchanger intended for at least two heat
exchanging fluids which comprises at least one plate package
manufactured by brazing together a number of thin walled heat
exchanging plates of an iron based material brazed by means of an
iron based brazing material, at which the heat exchanging plates
between themselves define plate inter spaces intended for the heat
exchanging fluids, at which the obtained brazing joints have a
metallurgical composition close to the composition of the iron
based plate material with locally higher amounts of B and/or P
and/or Si in and around the brazing joints in comparison with the
iron based plate material.
Description
[0001] The present invention relates to an iron based brazing
material for joining objects by brazing. The invention also
comprises a brazed product manufactured by brazing of objects of an
iron based material with an iron based brazing material according
to the invention.
[0002] Different steel or iron based materials are usually joined
by brazing with Ni-, Ag- or Cu-brazing materials.
[0003] Brazing is a process for tightening/joining, at which the
temperature is lower than the solidus temperature of the base
material of the objects which are to be joined
together/tightened.
[0004] Brazing materials consist of material for joining and
tightening, which completely or partly melt during the brazing
process.
[0005] U.S. Pat. No. 4,135,656 relates to a Ni-based alloy which
contains, counted as percentage by weight, 19-23% Mn, 5-8% Si, 4-6%
Cu, 0.6-1.8% B and balance with Ni apart from smaller amounts of
other elements. U.S. Pat. No. 4,314,661 describes another kind of
Ni-based alloy which contains, given as a percentage of atoms 0-4%
Fe, 0-21% Cr, 0-19% B, 0-12% Si, 0-22% P and balance with Ni.
[0006] When brazing with Cu one generally uses pure or almost pure
Cu. The pure copper brazing material has a well defined melting
point, while nickel brazing materials depending on the fact that
they are alloys often have a melting interval.
[0007] When joining plates of stainless steel in plate heat
exchanger copper brazing materials are often used. Copper is
however not suitable for all kinds of applications. The use of
brazing materials of copper for food applications is not allowed,
but it is used in plate heat exchangers for district heating and
for tap water installations.
[0008] Heat exchangers joined with brazing material of nickel are
used in many applications and are also allowed for a limited number
of food applications.
[0009] If brazing materials containing nickel alloys are used for
joining objects of iron or non nickel-based materials, the
composition of the brazed joints differs significantly from the
composition of the materials, which are joined. This can result in
undesired differences in the chemical and mechanical
properties.
[0010] The present invention offers possibility to join objects by
means of brazing by using a brazing material with mainly the same
composition as the base material used for producing the product, at
which the brazing material contains additive elements which lower
its liquidus temperature. Consequently, the present invention
offers a possibility to produce an apparatus as a plate heat
exchanger, which is compatible with food application requirements
by using a brazing material according to the invention. The
invention is mainly characterized in that the brazing material
consists of an alloy which apart from iron contains 0-40% Cr,
preferably 9-30% Cr, 0-16% Mn, preferably 0-8% Mn, and even more
preferably 0-5% Mn, 0-25% Ni, 0-1% N and maximally 7% Mo and below
6% Si and/or 0-2% B, preferably 0-1.5% B and/or 0-15% P all stated
as weight percent, which addition of boron, phosphorous and silicon
in combination or separately lowers the liquidus temperature, that
is the temperature when the brazing material has melted completely.
The iron content in the brazing material is suitably at least 50%.
The brazing material according to the invention must always contain
Fe and Cr.
[0011] The effective, working amount of B and/or P and/or Si should
lie in the interval given above in order to obtain the desired
lowering of the melting point. The analysed amount of Si may
however be considerably higher, since Si may occur for example in
the state of silicon carbides or silicon nitrides, be bonded to
oxygen or sintered in some other way. For the same reason the
analysed amount of B or P may be higher.
[0012] The iron based brazing material may contain alloying
elements as Ti, W, Al, Cu, Nb, Ta, V and others. Variations in
composition may also be a consequence of small inevitable amounts
of contaminating elements as C, O and S.
[0013] Melting point lowering elements are advantageously added to
the brazing material in amounts according to the following
formula
Index=%P+1.1.times.%Si+3.times.%B,
[0014] where the value of the Index should be 4.5-18.
[0015] The iron based brazing material is with advantage produced
by gas- or water atomisation of an ingot with a composition as
mentioned above or crushing such an ingot. Another alternative
method for manufacture is melt spinning.
[0016] The invention also comprises a brazed product produced by
brazing together iron based objects, by which the product is
characterized by the joining of the objects with an iron based
brazing material which is an alloy containing liquidus lowering
elements as B and/or P and/or Si. The composition of the iron based
brazing material is with advantage the composition as stated in the
main claim.
[0017] Both the iron based objects in the brazed product and the
iron based brazing material advantageously contain 9-30% Cr.
[0018] The brazed product is with advantage a brazed plate heat
exchanger intended for at least two heat exchanging fluids which
comprises at least one plate package manufactured by brazing
together a number of thin walled heat exchanging plates of an iron
based material by means of an iron based brazing material. The heat
exchanging plates define between themselves plate inter spaces
intended for the heat exchanging fluids. The brazing joints
obtained have a metallurgical composition close to the composition
of the iron based brazing material with locally higher amounts of
B, P, Si in and around the brazing joints in comparison with the
iron based plate material.
[0019] For brazing of iron based materials one has traditionally
used Cu- or Ni-brazing materials as mentioned earlier.
Surprisingly, it has now been found that one may start with a base
material with the same composition as the material in the objects
one desires to join. By alloying such a material with silicon
and/or boron and/or phosphorous one may obtain well functioning
brazing materials. By studying binary phase diagrams for pure iron
and Si, B and P one may find that a Fe--Si alloy has a melting
point minimum of 1212.degree. C. for about 19% Si. For a Fe--B
alloy there is a melting minimum at about 1174.degree. C. at about
4% B. In the Fe--P-system there is a melting minimum at about
1048.degree. C. at about 10% P.
[0020] In most cases pure iron materials are not used but instead
alloys are used, which apart from Fe also contains relatively large
amounts of Cr and Ni. In many alloys there are also Mo and Mn. To
try to theoretically establish the effect of addition of different
amounts of boron and/or phosphorous and/or silicon to such alloys
by using phase diagrams is almost impossible, since the number of
dimensions will be as large as the number of elements in the
alloy.
[0021] In order to obtain a brazing joint the liquidus temperature
of the brazing material should be below 1230.degree. C., preferably
below 1200.degree. C.
[0022] Surprisingly enough it has been found that an addition of a
relatively low amount of silicon, boron or phosphorous in
combination or alone may give such a lowering of the liquidus
temperature that a suitable brazing material may be obtained.
[0023] In the table below different examples of compositions of
brazing material according to the invention are given.
1TABLE 1 Analysis of the composition of some melts % % % % % % % %
Melt Fe Cr Mn Ni Mo Si B P C Index 1 Bal 16.8 1.5 11.8 2.2 4.4 0.5
6.1 0.1 12.4 2 Bal 16.7 3.7 11.7 1.9 1.0 0 10.6 0.1 11.7 3 Bal 17.0
1.8 12.1 2.1 1.0 0 10.1 0.1 11.2 4 Bal 17.1 3.0 12.0 2.2 4.7 0 6.0
0.1 11.2 5 Bal 17.0 2.9 11.8 2.1 5.6 0 6.0 0.1 12.2
[0024] The expression Bal (balance) means that the remaining
material in the melt consists of Fe.
[0025] The samples were brazed at a temperature of 1190.degree. C.
The result of the visual examination of the test brazing of the
samples was that all samples had melted and brazing joints had been
obtained, also mechanical strength was obtained for all joints.
[0026] The brazing material according to the invention is suitably
made in the form of a powder or a foil. The powder may be
manufactured by producing an ingot, which is thereafter crushed and
milled. The brittle nature of the material is utilized by this
manufacturing method. The disadvantages of ingot casting is that a
certain risk for segregation may yield a non-homogenous material
with a melting interval which is difficult to define or is broad.
For smaller ingots and/or rapid cooling the risk for segregations
is reduced. In ingot casting it is important to minimise the
contact with air by using vacuum casting or casting with a
shielding gas. As a consequence of the mechanical treatment the
energy content of the brazing material increases and with that its
reactivity.
[0027] Further manufacturing methods to produce a powder with a
homogenous composition consist of water or gas atomising. The
properties of the powder vary with the manufacturing method. The
crushed and milled particles are angular and pointed, the water
atomised are nodular and the gas atomised are almost spherical.
This difference in particle shape gives the brazing material
somewhat varying properties when used for brazing. By choosing
different atomising methods and the extent of crushing/milling
combined with screening, the distribution of the particle size may
be controlled. In water atomising the oxygen content generally will
be higher since water atomising takes place at a higher oxygen
potential than gas atomising. A higher oxygen content may give rise
to formation of oxides in the material which may have a negative
influence on the mechanical properties of the brazing joints. The
effective Si and/or B and/or P percentage in the brazing material
will consequently be lower, which means that the melting interval
will be displaced.
[0028] Manufacture of a foil by melt spinning from a metal melt
takes place by letting the metal melt be cooled directly against a
cold surface in such a way that a foil for example is formed. In
normal continuous foil production the cold surface consists of a
cold roll manufactured of copper or an copper alloy. It is also
possible to obtain amorphous foils, in such cases boron is
generally added.
[0029] The brazing material according to the invention may be
applied on the places where one desires a brazing joint by means of
different methods. A powder of brazing material manufactured by
means of any of the described methods may be suspended in some
binder in order to be applied in a suitable manner.
* * * * *